Sheet felt

ABSTRACT

This invention concerns a light weight sheet felt material suitable for use as roof and siding underlayment and insulation board facing which comprises on a dry basis 
     (a) 60-80 wt. % cellulose fibers; 
     (b) 15-30 wt. % glass fibers having a diameter of 5 to 16 microns and a length of 3/8-3/4 inch; 
     (c) 4-10 wt. % binder and 
     (d) 0.5-10 wt. % non-asphaltic, sizing agent having a flash point above 150°F. and an evaporation rate less than one which is selected from the group consisting of anionic rosinous and amphipathic ester and anhydride sizes and mixtures thereof. 
     The felt of this invention is of considerably lighter weight and higher porosity than other felting materials used for the same purpose and can be supplied in longer continuous sheet rolls than heretofore practical from a standpoint of handling, shipping, storage, and installation. Also the present sheet felt can be produced on conventional felt making equipment in a one step process.

This is a continuation of Ser.No. 08/552,901, filed Nov. 3, 1995; nowU.S. Pat. No. 5,717,012.

BACKGROUND OF THE INVENTION

The invention relates to felt sheeting suitable for use as siding androofing underlayment or as facing for conventional closed cell foaminsulation boards. Prior products for the same use are typically madefrom compositions of asphalt and cellulose/glass fiber of mixed lengthcontaining primarily glass fibers of 1/4 inch length and 15-20 microndiameter. However, serious problems are encountered in the manufactureof such felts since asphalt, when added to the composition, gums in theequipment necessitating frequent shut downs for cleaning. Additionally,the low fiber aspect ratios (fiber length divided by fiber width), ofthe glass filaments in prior felts has led to glass fiber balling intoobjectionable lumps which disrupt sheet formation and decreaseproduction rates.

Previously it was believed that glass fibers suitable for roofing andsiding required a thickness of greater than 15 microns for strength anda length of 1/4 inch or less for good porosity. However, it is nowdiscovered that such fibers are brittle and form glass balls duringdispersion in the felt making process.

Since it is common practice to wind felts produced in a felt mill inroll sizes suitable for handling and shipping, serious considerationmust be given to the weight of the felt and convenience of the consumer.Thinner, more pliable rolls of greater length which avoid frequentpatching and less waste are to be desired. Unfortunately, these aimshave not been achieved without sacrifice of other desirable propertiessuch as tear strength, low porosity and tensile strength.

Previous products also suffer from poor dimensional stability, i.e. agrowth in product dimension when exposed to moist conditions due tocellulosic water absorption.

Accordingly, it is an object of this invention to provide a lighterweight sheeting felt suitable for roof and siding underlayment andinsulation board facing which not only retains significant beneficialproperties but which additionally achieves higher porosity, greater tearstrength and better foam adhesion while overcoming the abovedisadvantages of equipment fouling and formation of glass balls.

Another object of the invention is to provide significant cost reductionin the commercial production of sheeting felts.

These and other objects and advantages will become apparent from thefollowing description and disclosure.

THE INVENTION

In accordance with this invention there is provided a non-asphalticsheeting felt composition and product consisting essentially of, on adry basis,

(a) 60-80 wt. % cellulose fibers;

(b) 15-30 wt. % glass fibers having a fiber diameter not in excess of16.5 microns and a fiber length of 3/8 to 3/4 inch;

(c) 4-10 wt. % binder for said fibers and

(d) 0.5-10 wt. % non-asphaltic, sizing agent having a flash point above150° F. and an evaporation rate less than one which is selected from thegroup of anionic rosinous sizes and amphiphathic sizes, e.g. C₁₆ to C₃₀ester and anhydride sizes and mixtures thereof.

In a preferred embodiment, the binder is a SBR^(*) latex, the cellulosefibers are derived from newspaper and corrugated kraft wastes containingat least 50% fibers of 1.5-3.5 millimeter length and 0.8-2.5 wt. %sizing agent. It is also desired that the sheeting composition containglass fibers having a fiber aspect ratio of between 600 and 1450. Theglass filament diameter of the present composition is critical topliability and superior tear strength and the fiber length is criticalto avoidance of glass ball formation during felt manufacture. Of theconventional glass filaments listed in following Table I, only thosehaving a diameter between 5 and 16.5 microns, i.e. filaments D-M, aresuitable for this invention. Although fiber M is usable, its greaterthickness tends to increase brittleness and thus is subject to breakageduring severe mixing conditions. Accordingly for fiber M, mild andshorter mixing periods are recommended in order to avoid lower fiberaspect ratios resulting from breakage. Filaments below class D are muchmore expensive to produce and do not possess the desired fiber strengthfor use in the present felts. Consequently, the diameter fibers ofclasses G-K are most preferred and fibers having a diameter betweenabout 8.8 and about 14μ and a length of 3/8-3/4 inch are preferred.

                  TABLE I                                                         ______________________________________                                        AVAILABLE FILAMENT DIAMETERS                                                  Filament                Diameter (microns)                                    Class     Min.          Ave.   Max.                                           ______________________________________                                        A         1.52          2.03   2.54                                           B         2.54          3.19   3.81                                           C         3.81          4.45   5.08                                           D         5.08          5.72   6.35                                           E         6.35          6.99   7.62                                           F         7.62          8.26   8.89                                           G         8.89          9.53   10.16                                          H         10.16         10.80  11.43                                          J         11.43         12.07  12.70                                          K         12.70         13.34  13.97                                          L         13.97         14.61  15.24                                          M         15.24         15.88  16.51                                          N         16.51         17.15  17.78                                          O         17.78         18.42  19.09                                          P         19.09         19.69  20.32                                          Q         20.32         20.96  21.59                                          R         21.59         22.23  22.86                                          T         22.86         23.50  24.13                                          U         24.13         24.77  25.40                                          ______________________________________                                    

An important beneficial aspect of the present invention is the lowweight of the felt product, i.e. 15-23 lbs/480 square ft. By reducingthe sheet weight and increasing the percentage of fiberglass, the amountof cellulose is appreciably reduced which provides a product ofsignificantly improved dimensional stability. Weight reduction aloneusually leads to an unacceptable decrease in tear strength.Unexpectedly, use of the present composition, with increased percentageof glass fibers, particularly the longer glass fibers, providesdesirably high tear strength in the light weight sheet felt.

The present felt sheet is economically prepared by providing an aqueousslurry of the above composition (a)-(d), forming a sheet in a feltingmill, pressing, draining and drying the resulting sheet for subsequentwinding in a suitable roll size. Because of the lightness and pliabilityof the present sheeting material, larger roll sizes based on weight of15 to 23 lbs/480 square feet can be easily handled; whereas most priormaterials having a weight of 27 lbs. or more/480 square feet are limitedto smaller roll sizes resulting in frequent seams and patching uponinstallation. As underlayment or as facings on a foamed core, the feltsheet thickness can vary between about 0.3 and about 4 mils althoughthicker sheets can be used for certain applications when desired. Thebenefits of increased feet per roll, e.g. an increase of up to 33%lineal feet per roll, are realized in reduced shipping costs and fewerproduction spicing for the consumer.

As facing for an insulation board, the rolled felt sheet of theinvention, prepared on paper line, is sent to insulation manufacturingwhere a foam precursor chemical or chemicals are poured onto an unrolledlower facer of the felt sheeting. As the foam spreads it enters alaminator where it rises to contact the a restricted upper face of thefelt sheeting and hardens thereon, after which the resulting sheet maybe cut into boards. Due to the reduced thickness of the present feltsheeting, a significantly faster more even foam chemical flow isobserved and an increased on-line curing rate through the thinner facersheet is achieved. It is also observed that the higher porosity of thepresent felt sheeting provides significantly stronger adhesion to thefoam core while avoiding appreciable bleed-through in highly functionalcores such as those composed of polymeric isocyanate. Surprisingly, thethinner felt sheets, employing higher aspect ratio of glass fibers asherein described, provide significantly increased tear strength and upto 50% improved dimensional stability.

The felt of the invention is especially useful as felt facer for rigidfoamed insulation boards such as are used in forming built-up roofing(BUR) on roof decks and as foam insulation sheathing used on siding.Such boards have a core of conventional rigid closed cell foam material,the cells of which normally contain hydrofluorocarbons or hydrocarbongases. Depending upon the intended use, such boards normally have corethicknesses between about 25 and about 100 millimeters. Boards of theinvention may be made in a conventional manner with the rigid foampreferably being formed and cured in contact with felt of the inventionso that the resulting facing is continuously adhered to the rigid foamcore. However, it is possible to form the core without a facing and thenbond one or more facings to the core using suitable adhesives. Ingeneral, the teachings of U.S. Pat. No. 4,351,873, are applicable to theformation of rigid foam cores and adhesion of facer to at least one faceof such cores. The distinguishing characteristic of insulation boards ofthe present invention is use of felt of the invention as a facer onconventional rigid foam cores. Polyurethane or polyisocyanurate foamsare most commonly used although other foamable polymers known for use insuch boards are also suitable. These include polyvinyl chlorides, ureaformaldehydes and melamine polymers, polystyrene, polypropylene,polyethylene, epoxy resin, acrylonitrile-butadiene-styrene copolymer,cellulose acetate, etc. Rigid foam cores of this type are well known andare described in a number of patents including U.S. Pat. No. 4,351,873,the disclosure of which is incorporated herein by reference.

Generally, facers used on conventional foamed insulation boards have notbeen economical and tend to have weak foam core adhesion. This hasresulted in various problems, especially in the manufacture of built-uproofing (BUR). In applications such as BUR, foamed insulation boardsfaced with conventional asphalt saturated felt are prone to warping due,at least in part, to facer dimensional instability and, when the boardis mopped with hot asphaltic materials, the facer has been known todelaminate from the foam core. Conversely, when the felt product of thisinvention is used as a facer for a foamed insulation board, theinsulation board is much less susceptible to warping at varying humidityconditions. Further, the present facer, having strong adhesion to thefoam, is resistant to delamination under all conditions and particularlywhen the board is mopped with hot asphalt in a finishing process. Feltand insulation board products of this invention also have a wide sphereof application in roofing systems where material compatibility isnecessary. For instance it is generally considered unacceptable to allowdirect contact between insulation board faced with conventionalasphalt-containing felt facers and a single ply polyvinylchlorideroofing membrane due to plasticizer migration. The insulation boardfaced with felt of this invention presents no problems with respect toplasticizer migration since it contained no asphalt.

Further, conventional asphaltic felt facers of lower glass fiber aspectratios which have been employed for insulation boards, have poorer fireresistance and do not retain sheet skeletal integrity when burnt;whereas insulation boards faced with felt of this invention have greatlyimproved fire resistance characteristics due to lower fuel value perunit area and greater sheet integrity after burning. Thesecharacteristics are especially desirable on facers of foamed insulationboards in BUR systems.

Additionally, conventional underlayment material of the asphaltic typeis generally deficient in porosity and frequently does not allowdesirably high transmission of water vapor needed to keep roof deckingand underlying insulation dry. Surprisingly the product of the presentinvention will transmit water vapor at about 10 to 20 times the rate ofconventional felt facer or underlayment material and at the same timewill remain as impermeable with respect to liquid water as theconventional products.

A common problem in using foamed insulation boards, especially thosewith polyurethane or polyisocyanurate foamed cores faced with asphaltsaturated felt facers, is that blistering of the facer can occur when itis mopped with hot asphalt at about 500° F. Such blistering takes theform of bubbles on the insulation board, thus enhancing the occurrenceof delamination from the polyurethane foam. In the manufacture ofurethane foam boards a very thin integral skin of polyurethane orpolyisocyanurate is formed between the facer and the actual foam matrix.The blistering occurs underneath the skin where the expanded gasescannot escape into the atmosphere and thus forms bubbles. In the presentinvention such blistering can be eliminated by perforating the boardsafter manufacture, i.e. after the boards have been foamed and facersaffixed. Such perforations are preferably in the form of small holes ofabout 0.02-0.1 inch diameter spaced apart from about 1/4 inch to about1-1/2 inches on centers and should be of sufficient depth so that boththe facer and the integral urethane skin are penetrated.

Cellulosic fibers suitable for use in products of this invention includeany of the cellulosic fibers commonly used in making cellulosic felt ofthe type conventionally used as underlayment and facer for insulationboards and may include for instance fibers derived from wood, paper,rags, etc. For economic reasons waste paper such as waste newspaper,waste kraft corrugated paper, etc. is frequently employed. Blends oflong and short cellulosic fibers are preferably used in order to providefelt of desired porosity. In this respect preferred blends containbetween about 25 and about 75 wt. % short fibers with between about 25and about 75 wt. % long fibers. Fibers of the type normally used inmaking newspaper are a suitable source of short fibers and fibers of thetype normally employed in making kraft paper can be the source of longfibers. Suitable short fibers normally have lengths between about 0.5and about 1.5 millimeters and long fibers normally have lengths betweenabout 1.5 and about 3.5 millimeters.

The binder used for the felt of the invention is employed in amountsbetween about 4 and about 10 wt. % based on dry felt composition withbetween about 4 and about 6 wt. % on the same basis being preferred.Suitable binders include for instance acrylamides, starch, urea resins,phenol resins, sodium silicates, epoxy resins, etc. Other suitablebinders include styrene/butadiene rubber (SBR) latex, as well asacrylic, neoprene, acrylonitrile or other natural or synthetic lattices.SBR latex is a preferred binder and, most desirably, is a carboxylatedtype of SBR latex substantially free of surfactants. One such preferredSBR latex is for instance one made by continuous monomer additionwithout the use of surfactant as taught for example by U.S. Pat. No.4,378,272, and incorporated herein by reference. Such a latex not onlyfunctions as a binder for the felt of the invention but can also act asan ionic exchange resin to aid in relieving the build up of certainundesirable materials in a closed water system for felt manufacture.However, other binders such as those mentioned above may be substitutedin whole or in part.

The sizing agent, which replaces the asphalt quota formerly employed infelt compositions, e.g. up to 20 wt. %, is bifunctional in that itsupplies both body and waterproofing to the present felt composition.Suitable sizing agents have a flash point above 150° F. and are highlystable having an evaporation rate less than 1. More specifically, thesizing agent of the present composition is described in WET ENDCHEMISTRY, AN INTRODUCTION by William E. Scott, Chapter 4. "InternalSizing", pages 23-27, published by TAPPI PRESS, 1992, which disclosureis incorporated herein by reference. The sizing agents disclosed in thetext include acidic and alkaline, fortified, e.g. maleic anhydridefortified, and non-fortified organic sizing materials having a pH offrom about 3.5 to about 10 and an acid number of from 0 to about 200,which materials have superior resistance to water penetration. Thesizing component of the present invention is introduced into thecomposition as an aqueous dispersion, suspension, colloid or emulsionhaving a solids content of between about 30 and about 70%, preferablybetween about 40 and about 60%, and is present in the total compositionof the preformed felt sheet at a concentration of from about 50% toabout 80 wt. %, preferably from about 60 to about 70 wt. %.

Generally the sizing component is a mixture of an acidic compound, e.g.alum, and a rosin derived from gum, wood or tall oil. These rosinscontain normal and isomeric mixtures of abietic and/or pimaric acids ina fortified or non-fortified condition. Other suitable sizing materialsinclude amphipathic cellulose reactive compounds which contain C₁₆ toC₃₀ hydrocarbon chains such as, for example, an alkylketene dimer, analkenyl succinic anhydride and mixtures of the above or intermixtureswith rosin/alum. Commercially available ALPHASIZE®, supplied by AmericanCyanamid Co., is an example of a preferred anionic sizing agent employedin this invention. Alternatively, an alkaline component, can besubstituted in whole or in part for the acidic component to providecationic sizing agent suitable for the composition. Such sizing agentsgenerally have a pH of from abut 7 to abut 10 and are resistant to acidand alkaline penetrants. However, these cationic agents are subject todeterioration and compositions containing them should not be stored overextended periods.

The sizing agent employed in the felt composition obviates fouling ofequipment in the preparation of the felt and contributes to the lighterweight of the felt material, thus permitting end product rolls ofsignificantly longer length. It is also observed that replacement of theconventional asphalt component with the present size unexpectedlyprovides for faster on-line production and more even and rapid spread ofcore compositions over the felt facing.

In addition to the required ingredients of the felt compositiondescribed above, other conventional adjuvants used in felt manufacturemay also be included. For example conventional flocculants, defoamingagents, precipitants, etc. may be included. Illustrative of suitableflocculants are high molecular weight cationic acrylamide polymer suchas Betz 1260, which may be used in amounts of between about 1/2 lb. andabout 8 lbs. per ton of dry felt. Representative precipitants optionallyemployed herein include multivalent metal salts or synthetic polymers.Pigment may also be used for optional coloring of felt of the invention.A preferred pigment is carbon black which can be fixed onto the matrixof the felt with multivalent salts or polymeric flocculants. Desirablyany pigment used should not leach out when the finished product issoaked in water for prolonged periods of time. Many other modificationsand additions to the present felt sheet formulation will become apparentfrom this disclosure.

Having generally described the invention, reference is now had to thefollowing examples which illustrate a preferred embodiment and comparethe present composition with a conventional sheet felt composition.However, the example is not to be construed as limiting to the scope ofthe invention as more broadly described above and as defined in theappended claims.

EXAMPLE

Felt sheets are produced on a commercial paper making equipment byforming a felt sheet from an aqueous slurry of the followingformulations (A and B), pressing the formed sheet and allowing the sheetto drain for about 3 minutes before drying at a temperature of about300° C.

                  TABLE A                                                         ______________________________________                                        FORMULATION       A                B                                          ______________________________________                                        Glass Fiber                                                                   Diameter          M*               K                                          Average fiber length (inch)                                                                     1/4              1/2                                                          WEIGHT PERCENT                                              Glass fiber       13.0      ∓1  18.0                                       Waste Newsprint   39.5      ∓2  37.0                                       Waste Kraft corrugated                                                                          39.5      ∓2  37.0                                       SBR latex         5.0       ∓1  5.0                                        Asphalt (50% solids emulsion)                                                                   1.0       ∓0.1                                                                              --                                         ALPHASIZE 120     --        ∓0.1                                                                              1.0                                        (50% solids emulsion)                                                         Carbon black dye  2.0       ∓0.1                                                                              2.0                                        Alum              70.0 + 5.0 lbs/ton of felt                                  Flocculent         2.0 + 5.0 lbs/ton of felt                                  Glass Ball Formulation in                                                     in-line process                                                               No. of balls after 8 hours                                                                      200              10                                         ______________________________________                                         *based on U.S. Pat. No. 4,543,158                                        

The characteristics of the above dried felt sheets are reported infollowing TABLE B.

                  TABLE B                                                         ______________________________________                                        FORMULATION           A      B                                                ______________________________________                                        Weight (lbs/480 sq. ft.)                                                                            27.0   19.5                                             Caliper (1/1000 inches)                                                                             23.0   17.0                                             Tear strength CMD* (grams-force)                                                                    301    340                                              % Ash Content*        17.6   23.5                                             % Expansion CMD       1.0    0.5                                              Foam Adhesion (lbs/sq. inch)                                                                        8.0    10.0                                             Linear feet/roll      6,600  8,700                                            ______________________________________                                         *higher ash % indicates better fire resistance                           

higher ash % indicates better fire resistance

What is claimed is:
 1. An insulating board having a foam core laminatedto a felt sheet having the composition of a light weight feltcomposition suitable for siding and roofing underlayment and insulationboard facing which comprises, on a dry basis,(a) 60-80 wt. % cellulosefibers; (b) 15-30 wt. % glass fibers having a diameter not less than 5and not in excess of 16.5 microns and a fiber length of 3/8-3/4inch; (c)4-10 wt. % binder and (d) 0.5-10 wt. % of non-asphaltic water repellantsizing agent having a flash point higher than 150° F. and an evaporationrate less than one which is selected from the group of anionic/rosinoussizes and C₁₆ to C₃₀ amphipathic sizes and mixtures thereof.
 2. The feltof claim 1 wherein said binder is a latex.
 3. The felt of claim 2wherein said latex is SBR^(*).
 4. The felt composition of claim 1wherein the water repellant sizing agent is selected from the group ofanionic and cationic sizes and mixtures thereof.
 5. The felt compositionof claim 1 wherein the sizing agent is an alum/rosin sizing agent. 6.The felt composition of claim 1 wherein the concentration of the sizingagent in the total composition is between about 0.8 and about 2.5 wt. %.7. The felt composition of claim 1 wherein component (b) has a fiberaspect ratio of between about 600 and about 1450 and a filament diameterof from about 5 to about 16.5μ.
 8. The felt composition of claim 7wherein (b) has a filament diameter of from about 8.8 to about 14μ. 9.The felt composition of claim 1 wherein component (a) is a paper wastecontaining fibers of at least 50% of 1.5-3.5 millimeter length.
 10. Thefelt composition of claim 9 wherein the paper waste is a mixture ofnewsprint paper and corrugated Kraft paper having mixed fiber lengths ofbetween about 0.5 and about 1.4 mm short fibers and between about 1.5and about 3.5 mm long fibers.
 11. The felt composition of claim 1 inrolled form and having a weight of between about 15 and about 23 lbs/480square feet.
 12. The insulating board of claim 1 wherein said foamedcore is a polymer selected from the group consisting of urethane,isocyanurate, vinyl chloride, urea-formaldehyde and melamine, styrene, aC₂ to C₃ alkylene, epoxy, acrylonitrile-butadiene- styrene or celluloseacetate and mixtures thereof.
 13. The insulating board of claim 12wherein said foamed core is polyurethane or polyisocyanurate.